It has long been known to provide spot lights or directed lighting for stages, theaters, and other environments with the use of individual light sources hung from trusses or fixed structural members mounted adjacent to the area to be lit. Some light sources are used as wash or general area lighting, while other light sources are used as spot lights for highlighting specific positions on stage, portions of a performer's body or the like. In other applications, directable light sources are used to illuminate such environments as homes or offices.
Various devices are known in the art for changing the color of the light emitted from a light source. For example, light transmissive colored sheets or "gels" may be interposed in the light beam to change the color of the light. A variety of mechanical means exist for exchanging various differently colored gels in a single lighting instrument. Slide changers have long been used in high-powered spot light applications. Under the control of a human operator, the spot of light projected upon the stage follows the performer as he or she moves. The operator can also manipulate gel frames mounted on tracks such that one filter can slide into a position transverse to the light beam while another filter can slide out of the light beam, thereby changing the color of the beam.
More recent systems have been devised to exchange colored gels by means of a remotely-controlled, motorized mechanism. In one such system known as the scrolling gel changer, up to 16 or more colored gels are connected together by glue or adhesive tape in a side-by-side fashion to form a long strip of colored gels. The strip is then wound onto a supply reel, threaded through the mechanism so as to cover the forward aperture of a lighting instrument, and connected to a take-up reel. With a motor drive provided to rotate either the supply reel or the take-up reel, the gel strip can be wound or unwound so as to position the desired gel over the forward aperture, thereby changing the color of the light beam projected from the lighting instrument.
Other recent systems have been devised in which many parameters of a light beam projected by a lighting instrument can be varied by remote control, including the orientation of the instrument with respect to azimuth and elevation, the diameter of the beam, the shape of the beam, the divergence of the beam, as well as the color and intensity of the beam. U.S. Pat. No. 4,392,187 by Bornhorst typifies such automated systems. Bornhorst '187 discloses computerized remote control of automated lighting instruments having motorized mechanisms for varying the aforementioned parameters of the light beams. Bornhorst '187 achieves color control by means of positionable dichroic filters rather than the gels mentioned above.
Another example of a dichroic-filter color changer is disclosed in U.S. Pat. No. 4,602,321 by Bornhorst, wherein three filter sets each include three pivotable dichroic filter elements. Each filter element is rotatable around an axis perpendicular to the light beam in order to vary the angle of incidence and thereby vary the hue of the light beam. Rotation of the filter elements also varies the white light transmitted past the filter elements to vary the saturation of the light beam.
The present invention is directed to a lighting instrument having an improved color changing mechanism employing pivotable filters. The invention achieves improved beam color variation in a compact, modular assembly. Other improvements and advantages will be apparent from the following description of the invention.